Not Applicable
Not Applicable
1. Field of Invention
This invention relates to bag closures, specifically reusable closures which are used for closing the necks of plastic bags, and especially to bag closures of the type generally comprising two separate but complementary elongated members which trap the flattened neck of said bag between them when mated.
2. Description of Prior Art
Bags formed of polyethylene or other plastics are commonly supplied to grocery shoppers for holding produce. Similar bags are available for separate purchase, and are useful in storing groceries and other materials; and various consumer goods are packaged in such bags.
Bags containing pre-packaged goods are often heat-sealed or closed in some other permanent manner when the consumer receives them. However, if the entire pre-packaged contents are not removed from the bag at its first opening, then the consumer must reseal the bag between openings. If repeated access to the bag contents is desired, a reusable bag closure is required.
Various solutions to this dilemma have been produced over the years, in many forms. For example, twist ties with a wire core, which are twisted around a gathered bag neck, are one of the oldest and lowest-cost solutions. However, such wire ties require a substantial xe2x80x9ctwistingxe2x80x9d motion to apply, and must be tightly wound in order to form a tight closure; in fact, it is difficult to make a water-tight seal with a wire tie. And wire ties quickly become damaged and unsightly with use, unlike a true reusable bag closure. Even new, a wire tie is rather unsightly, and can sometimes have a protruding wire end that can poke the user or the bag.
Other low cost bag closures have been produced, including an assortment of related small, flat closures, generally made of frangible plastic, which trap a gathered bag""s neck within a notch or otherwise confine the neck of the bag in a bunched or gathered state. However, this type of closure can be reused only a few times, since it is generally bent or twisted when removed. Also, these closures are easily lost or misplaced. And since the bag neck is gathered when closed, it is difficult to form a reliable xe2x80x9cwater-tightxe2x80x9d seal with this type of closure, as well.
There is another class of bag closures with superior performance, which clamp a bag neck over the entire bag width when it has been smoothed and flattened, making a more positive seal possible. Of course, such closures are larger and more expensive to produce than the xe2x80x9cthrow-awayxe2x80x9d closures discussed previously. But bag closures in this category are also generally more durable, suitable for indefinite use, so a somewhat greater cost is acceptable. And the appearance of this type of bag closure is generally neater and more appealing. Consumers are willing to pay a somewhat greater price for a superior bag closure which provides a better seal and a neater appearance, and which can be used indefinitely.
Various mechanisms can be used in such closures for clamping the flattened back neck; in fact, the concept of trapping flattened thin fabrics or other flexible sheet materials between two linear members has been used for a long time. For example, U.S. Pat. No. 1,362,651 to Towns in 1920 described a method of trapping a flat section of canvas material between a tubular rib and a spring metal xe2x80x9ccasexe2x80x9d having a substantially C-shaped cross-section with an inner radius approximately equal to the outer radius of the rib. Although Towns intended his invention for use primarily in farm machinery, many bag closures have been designed which use essentially this same mechanism.
For example, U.S. Pat. No. 3,141,221 to Faulls describes a closure for flexible bags comprising two separate but complementary elongated rigid members which trap a flattened bag neck between them when mated. This design closely resembles Towns"" canvas trapping mechanism, and provides a durable, truly reusable bag closure. But this type of bag closure is relatively expensive to produce, requiring the separate manufacture of two large parts. And making the closure a two-part assembly also requires the user to keep track of both sections between uses; if one section is lost, the entire expensive assembly is useless.
U.S. Pat. No. 3,266,711 to Song describes a similar closure with two separate members; however, Song goes on to describe an improved version of the closure, wherein the two primary members are joined together by a link or hinge formed from the same plastic or other material which forms the two complementary members. However, Song""s bag closures still require a manufacturing process wherein each bag closure is created separately (albeit in a single operation for the hinged version) by molding the material which forms the closure. And Song explicitly teaches that the interior diameter of the female member must always exceed the exterior diameter of the male member, which creates an implicit limit on the materials which may be used to form a closure according to Song.
More recently, other designs have been made which connect the two sections of such a bag closure. For example, U.S. Pat. No. 4,296,529 to Brown shows a one-piece hinged bag sealing device comprising paired linear strips which trap the flattened bag neck when the hinge closes, and further comprising a locking clasp at the far ends to lock the hinge closed. Further, U.S. Pat. No. 5,379,489 to Delk et al. shows a similar hinged assembly wherein the trough-like shape of one member fits over the bladelike opposing member, trapping the bag neck, again with a separate locking mechanism. And U.S. Pat. No. 5,713,108 to Solomon et al. shows a bag closure comprising a pair of rigid linear members called the locking arm and the receiving arm, also joined at a hinge and having elongated seating shoulders for interlocking engagement, obviating the need for a separate locking clasp. These designs do advantageously eliminate the need for multiple separate pieces, so that a user is not required to keep track of them. Solomon""s design even eliminates the need for a separate locking mechanism. However, all are still relatively expensive to produce, since they require the separate manufacture of several components which must then be assembled. And these closures"" common rigid, elongated hinged design is inherently weak, having a tendency to break at the hinge if inadvertently stressed in the opened state. This problem leads to premature failures if these closures are made from commonly-available low cost materials; or alternatively, if they are made from stronger metals, it leads to even greater cost.
U.S. Pat. No. 5,664,296 to May shows a bag with a built-in closure where the two separate complementary members, again circular and C-shaped in cross sections, respectively, are mounted directly to opposing inside faces of the bag. The concept embodied in this invention is revolutionary and has led to the tremendously popular xe2x80x9czipperxe2x80x9d type of plastic bags which are quite common today. This approach combines the bag and the bag closure into one, and essentially creates a new product, the xe2x80x9czipper bagxe2x80x9d, which competes directly with simpler bags without built-in closures. For some types and sizes of bags, the zipper bag has since become dominant. However, the zipper bag has not and will not become universal, because of the following limiting factors: 1) The zipped closure does not form a strong enough seal for some uses; 2) the zipper closure manufacturing process is not always compatible with the bag manufacturing process; 3) the zipper closure must be produced for an extremely low cost, comparable or less than the cost of producing the bag, in order to be practical; and 4) even with such a low manufacturing cost, a zipper bag is still costlier to produce than a similar bag without such a closure.
Thus, although the new zipper bag type is extremely popular, these factors dictate that plastic bags without such built-in closures will still be used for the foreseeable future. For example, it appears that adding zipper type closures is impractical or adds substantially to the price of bags made out of certain less flexible xe2x80x9ccracklyxe2x80x9d types of plastics, which are much favored by manufacturers for their ability to carry colorful advertising and labeling, zipper closures are rarely seen on this type of bag. And some types of plastic bags are just not practical to produce with zipper closures. For example, the produce bags most common in stores today are made of strong but extremely thin plastics. These bags are much thinner than the plastics generally used to produce a zipper closure. Even if it were feasible to connect such a bag to a zipper closure, there would likely be more plastic in the zipper than in the whole bag, making such an amalgam not cost-effective. And zipper closures have a typical strength which may not be great enough for larger or heavier contents, many manufacturers continue to package their products using heat-sealed bags, since the heat-sealed closure is typically similar in strength to the bag itself. Finally, when using the bag for storing foodstuffs, keeping the xe2x80x9czipperxe2x80x9d clean and sanitary, as it must be since it is mounted inside the bag opening, becomes a problem for repeated use.
Accordingly, several objects and advantages of the present invention are:
1. To provide a bag closure which traps a flattened bag neck, providing a tight seal.
2. To provide a durable bag closure which can be reused indefinitely.
3. To provide a bag closure with a simple one-piece hinged construction.
4. To provide a hinged bag closure wherein the hinge is not subject to breakage if stressed when opened.
5. To provide a simple hinged bag closure which can be manufactured for lower cost than other hinged bag closures.
6. To provide a simple hinged bag closure which can be manufactured more quickly and easily than other hinged bag closures.
7. To provide a simple hinged bag closure which may be easily cleaned.
8. To provide a simple hinged bag closure which provides means for orderly storage of bagged materials.
A novel bag closure 100, advantageously formed from a single length of low-cost pliable yet resilient substantially-tubular hose comprises a first xe2x80x9cbasexe2x80x9d section 10 of unmodified hose, a second narrowed xe2x80x9cneckxe2x80x9d section 20 near the center of the closure, and a third xe2x80x9cclampxe2x80x9d section 30. Clamp section 30 may be formed by removing a narrow linear strip of hose material along a line substantially parallel with the cylindrical axis of the hose, thus leaving a section of hose with a substantially C-shaped cross section; the width of the removed strip is generally less than half of the circumference of hose section 30, so that section 30 will clamp over base 10. Hinge 20 is formed similarly, except that the removed strip represents a greater proportion of the hose material; in general, more than half of the hose material will typically be removed in neck 20, leaving only a narrow strip of material with a substantially parenthesis-shaped cross section joining sections 10 and 30. A bag neck may be sealed by laying the flattened bag neck across cylindrical base 10, folding the closure at its narrowed neck or hinge 20 and forcing clamp section 30 over the cylindrical base 10, trapping the bag neck between base 10 and clamp 30 and thus forming a tight seal.
Various topological variations of the basic tubular hose are discussed, offering potential ways to make the seal tighter, or ways to offset potential material limitations of the hose itself.
Finally, a manufacturing method is described that promises considerable savings in manufacturing costs, by making hinge 20 and clamp 30 complementary such that closure 100 and a second closure 200 can be cut from a single piece of hose, with little wasted hose material.